Coherent states of the 1+1 dimensional Poincaré group : square integrability and a relativistic Weyl transform S. Twareque Ali, J.-P. Antoine (1989) Annales de l'I.H.P. Physique théorique
Continuity of Locally Compact Group Actions with Measurable Orbit Maps. Dietrich Helmer (1980) Mathematische Zeitschrift